The present invention relates generally to leads for stimulating or monitoring tissue. More particularly, it pertains to a torque mechanism for an extendable and/or retractable lead.
Leads implanted in or about the heart have been used to reverse certain life threatening arrhythmias, or to stimulate contraction of the heart. Electrical energy is applied to the heart via the leads to return the heart to normal rhythm. Leads have also been used to sense in the atrium or ventricle of the heart and to deliver pacing pulses to the atrium or ventricle.
Cardiac pacing may be performed by the transvenous method or by leads implanted directly onto the epicardium. Permanent transvenous pacing is performed using a lead positioned within one or more chambers of the heart. One or more leads may be positioned in the ventricle or in the atrium through a subclavian vein, and the lead terminal pins are attached to a pacemaker which is implanted subcutaneously.
The lead includes a conductor, such as a coiled conductor, to conduct energy from the pacemaker to the heart, and also signals received from the heart. The lead further includes outer insulation to insulate the conductor. Currently, providing the lead with insulation is done by stringing silicone tubing over the lead. Stringing involves the use of chemicals which swell the silicone tubing, so that the coiled conductor can be pulled through the tubing. As the chemicals evaporate, the tubing contracts around the conductor. Stringing is a complicated manufacturing process which also can result in axial gaps between the conductor and the insulative tubing. The gaps contribute to an increase in the size of the lead body outer diameter.
One approach to implanting the leads permanently or semi-permanently is to include active or passive fixation elements with the leads. Active fixation elements, such as a helix, are rotated to screw the lead into the endocardial wall. To rotate the helix, the coiled conductor is rotated or a rigid stylet is removably disposed within the lead and rotated. As the coil is rotated, however, the shape of the coil opens and closes changing the pitch of the coil, and changing the amount of torque applied to the helix. As the stylet is rotated, the active fixation element sometimes jumps out of the end of the lead, resulting in potential damage to tissue and/or the helix, thereby frustrating the process of implantation. In addition, it is difficult for the implanter to determine how many turns to the stylet are necessary to advance the helix a certain distance.
Accordingly, there is a need for a lead which allows for a less complex manufacturing process and improved insulation. What is also needed is a lead having a smaller outer diameter. What is further needed is a lead which gives the implanter more control over the implantation process.
A lead assembly is provided which includes an insulative lead body extending from a proximal end to a distal end, and the lead body has one or more conductors disposed therein. The lead assembly further includes an electrode assembly including at least one electrode electrically coupled with the at least one conductor, where the at least one conductor includes at least one braided conductor, and the braided conductor is rotatable to extend and/or retract at least one electrode. At least one coating of insulation is coated directly on the braided conductor.
Several options for the lead assembly are as follows. For instance, in one option, a portion of the at least one coating is removed from the braided conductor to reveal an exposed portion of the braided conductor, and at least one electrode is electrically and mechanically coupled with the exposed portion of the braided conductor. In another option, the lead assembly further includes a second coating of insulation coated between the braided conductor and a second conductor, and the second coating is coated directly on the second conductor. In yet another option, the braided conductor comprises a torque transfer member.
In another embodiment, a lead assembly is provided which includes a flexible lead body extending from a proximal end to a distal end, the lead body including one or more conductors disposed therein, an electrode assembly including at least one electrode electrically coupled with at least one conductor, and a flexible torque transmission member extending from the proximal end to the distal end, the torque transmission member comprising a braided member rotatable to extend and retract a first electrode mechanically coupled thereto.
Several options for the lead assembly are as follows. For instance, in one option, the torque transmission member is non-removably disposed within the lead body. In another option, the lead assembly further includes a coating of insulation coated between a first conductor and a second conductor, where the coating of insulation is optionally coated directly on the first conductor. The lead assembly, in another option, further includes an outer layer of insulative coating, and an inner layer of insulative coating, wherein each insulative coating is coated directly on one of the at least one conductors, and optionally has a stripped portion where a portion of the outer layer is stripped from the conductor.
In yet another embodiment, a lead assembly is provided which includes a flexible, insulative lead body extending from a proximal end to a distal end, the lead body including one or more conductors disposed therein. The lead assembly has an electrode assembly including at least one electrode electrically coupled with at least one conductor. The lead assembly further includes a braided means for transferring torque from the proximal end to a first electrode, the means for transferring torque rotatable within the flexible, insulative lead body to extend and/or retract the first electrode.
Several options for the lead assembly are as follows. For instance, in one option, the torque transmission member is non-removably disposed within the lead body. In another option, the means for transferring torque is operably coupled at the proximal end of the lead body. In yet another option, the lead assembly further includes a first conductor and a second conductor, and a coating of insulation coated between the first conductor and the second conductor. The braided means for transferring torque, in one option, comprises an electrical conductor configured to conduct signals from the proximal end to the first electrode.
In another embodiment, a method is provided which includes braiding material to form a torque transmission member, mechanically coupling the torque transmission member with an extendable and/or retractable electrode, disposing the torque transmission member within a flexible lead body, and rotating the torque transmission member and extending at least one electrode.
Several options for the method are as follows. For instance, in one option, the method further includes coating insulative material directly on the torque transmission member. In another option, braiding the material includes braiding conductive material to form an electrically conductive torque transmission member. The method includes, in another option, braiding flexible material to form a flexible torque transmission member. Still further, in another option, the method further includes providing a conductor over and around the torque transmission member, and coating insulative material directly on the conductor.
In another embodiment, a method is provided and includes braiding two or more flexible conductors to form a first flexible, braided conductor, the first braided conductor extending from a first end to a second end. The method further includes coating insulative material directly on the first braided conductor, mechanically and electrically coupling at least one rotatable electrode with the first braided conductor, and disposing the first braided conductor within an outer insulative lead body. The method further includes rotating the first braided conductor and rotating the rotatable electrode, and coupling the first end of the first conductor with an energy source.
Several options for the method are as follows. For instance, the method optionally includes braiding multiple conductors to form a second conductor around the first flexible, braided conductor, and optionally further coating a second coating of insulative material directly on the second braided conductor. In another option, the method includes stripping insulative material from a portion of the first braided conductor, and exposing a portion of the first braided conductor.
The lead provides for a smaller lead body diameter due to the elimination of gaps, and tolerance stack-up of the assembly. The lead allows for the ability to start and stop tubing to allow for transition areas of the outer insulation, allowing for the device to have an isodiametric shape. Furthermore, the braided conductors have multiple intersections which offer improved flex fatigue properties. A further benefit is that the anode and cathode are not co-radial, the cathode is suitable for use as a driving mechanism for an extendable or retractable positive fixation lead.